/*
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is ST_EXT-S_UIMAST.
 *
 * The Initial Developer of the Original Code is
 * University of Rome, Tor Vergata
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
 */

package it.uniroma2.art.uimast.impl;

import it.uniroma2.art.ontapi.ARTResource;
import it.uniroma2.art.uimast.xpts.Variant;

import java.util.Iterator;
import org.w3c.dom.Element;

/**
 * A data source representing a literal value.
 * @author <a href="mailto:manuel.fiorelli@gmail.com">Manuel Fiorelli</a>
 */
public class ValueDataSource extends DataSource
{

	/**
	 * Constructs a <code>ValueDataSource</code> object.
	 * @param v the prototype variant (of the appropriate concrete class)
	 * @param lexicalForm the user provided lexical representation
	 * @throws Exception
	 */
    public ValueDataSource(Variant v, String lexicalForm)
        throws Exception
    {
        super(v);
        
        // Initializes the variant with the given lexical representatation.
        if(!v.setValue(lexicalForm))
            throw new Exception("Invalid lexical representation \"" + lexicalForm + "\"");
    }

    @Override
    public Iterator<Variant> apply(ARTResource domainObject, ARTResource annot)
    {
        return new Iterator<Variant>() {

            public boolean hasNext()
            {
                return !read;
            }

            // Gets the value.
            public Variant next()
            {
            	// Checks if the value was already read.
                if(read)
                {
                    throw new IndexOutOfBoundsException("Cannot dereference a past of the end iterator");
                } else
                {
                    read = true;
                    return v.clone();	// clones the prototype variant, to avoid unexpected behavior if the user stores it
                }
            }

            // The remove method isn't supported.
            public void remove()
            {
                throw new UnsupportedOperationException("Cannot delete elements from a read only sequence");
            }

            // Flag denoting if the value was read.
            private boolean read;
        };
    }

    @Override
    public void toDOM(Element e)
    {
        e.setAttribute("value", v.getLexicalRepresentation());
    }
}
